Method and apparatus for applying a fluid to heat-transfer surfaces



Get. 8, 1929. s, JACOBUS 1,730,461

METHOD AND APPARATUS FOR APPLYING A FLUID TO HEAT TRANSFER SURFACESFiled July 1925 2 Sheets-Sheet l INVENTOR ATTORNEY 5 Oct. 8, 1929. 5, cBus 1,730,461

METHOD AND APPARATUS FOR APPLYING A FLUID TO HEAT TRANSFER SURFACESFiled July 5, 1923 2 Sheets-Sheet 2 i l Hi 1 i t 5, if. D L w// /0 ,y

M f I W a & A. 3 /7 MW c 1 id YINVENTOR Md cream? our, NEW JERSEY,assrenoa 'ro THE nancocx & WIL- or BAYONNE, NEW era, a ooarona'rron ornew JERSEY TUS FOB APPLYING A FLUID T0 HEAT-TRANSFER SURFACESApplication filed July 5, 1923. Serial No. $9,469.

In the operation of heat-transfer devices in which a metallic surface iscontacted on opposite sides by two fluids, such as a gas and a liquid,or two gases, particularly when such heat-transfer devices .or heatexchangers are operated in connection with flue gases of steam boilers,there is liable to be a deposition of moisture from the gases on themetallic surfaces, and such moisture may also contain very dilute acid.This moisture, particularly if any acid is present, will eventuallydestroy the metallic surfaces. Furthermore, there is a liability fortar, soot and 'cinders to collect on the surfaces of the heat exchangerwhich are contacted by the flue gases, particularly on the coolerportions of the heat-exchanger surfaces.

By my present invention I propose to provide an apparatus and a methodby which the diificulties arising from the above-namedconditions' can bereadily remedied or prevented.

My present application is a continuation in part of my rior ap licationSerial Number 336,419, file Novem er 17, 1919, which was in turn adivision of my application Serial No. 244,685, filed Jul 13,1918.

My invention will e best understood from the followin description andthe annexed drawing of i ustrative forms of apparatus embodying myinvention and by which my method may be carried out. V

Inthe drawings, Fig. 1 is a longitudinal section, partly in sideelevation, of an illustrative steam boiler plant embodying my invention;Fig. 2 is similar to Fig. 1, but s owing a modification, and Fi 3 is avertical section on the line 3-3 of ig. 2, looking in the direction ofthe arrows.

Like reference characters indicate like parts in the several views.

In the arrangement shown in Fi 1, the boiler is of a well-known type inw ich the horizontally inclined water tubes 10 are connected to uptakeand downtake headers which, in turn, are connected to a transverse steamand water drum 11, the boiler having a furnace 12 and a superheater 13.

From the boiler the gases pass upward through a bank of tubes 15constituting a vertical economizer to which water is introduced throughthe pipe 16 by means of a pump 17 and passes to the steam and water drum11 through the pipe 18.

The gases on passing from the vertical economizer enter a chamber 19through which water is sprayed, this water being introduced theretothrough a pipe 20 and from this washing chamber, the water may flow to asettling tank and means for re-pumping the same, this tank andre-pumping means not being shown. When the water is circulated over andover again, a re-agent to neutralize the acid fumes absorbed by watermay be added. From the chamber 19 the gases flow to 'a chamber 21, inwhich is installed a lowpressure stage 22 of the economizer, thislowpressure stage having horizontally extending tubes connected byheaders in a well-known manner. The water for the. low-pressure stageenters through the pipe 23 and fiows back and forth through the tubes ofthe economizer to the upper header, from which it flows through the pipe24 to the pump 17. Above the economizer 22 I provide a spraying device25 supplied by a pipe 26, this spraying device being arranged so thatall of the tubes of the economizer 22 will be contacted with the sprayedliquid from the spraying device 25. Any of the sprayed liquid falling tothe bottom of the compartment 21 willbe caught in a funnel-shapedreceptacle 27, from which it may be drawn through a valve 28. A

forced-draft fan 29 operated by a motor 30 :serves to draw the gasesinto the flue 31.

The spraying device may be arranged to supply water for washing purposesonly, the minute streams of water being arranged to strike the exteriorsurfaces of the economizer tubes to wash off any accumulation of soot ortar, and this may be done without stopping the operation of the boilerand while the gases are flowing through the flue and water through theeconomizer. The spraying device 25 may be also used for supplying afluid-protective material, such as oil, asphaltum, pitch or the like,which, by its adherence to the exterior surfaces of the economizertubes, will provide a protective coating to prevent the corrosion of thetubes from the moisture a d acids ic y e c n a ned-in the the tubes andwill drop off or be slowly re-,

moved by the sweeping of the gases over the tubes, By providing acontinuous or a frequently renewed supply, however, the tubes are keptcontinually coated.

The excess of oil or other coating material may be drawn off through thevalve 28.

By spraying the gases in the chamber 19, I not onl preliminarily washthe gases but secure a better heat transfer rate to the economizer,because it is well known that the rate of heat transfer from steam orliquids to a cooler surface, such as a tube wall, is much higher thanthe rate of transfer from gases at the same temperature to the samecooler surfaces. gases to the tubes, due to the introduction of watervapors in the gases more than compensates for any slight reduction intemperature that may take place. This preliminary washing, however,loads the gases with water and without some protective arrangement, suchas I have provided, the deterioration of the economizer surfaces mightbe more rapid than if no spraying in the chamber 19 took place. W

In Figs. 2 and 3 I- have shown an arrangement in which my invention isapplied to a boiler having an air heater, the heated air from which maybe .utilized in any suitable manner, preferably by being returned to thecombustion chamber, so that the heat of the flue gases is returned tothe boiler system.

The arrangement heretofore described is precisely the same except thatin the chamber 21, I have provided an air heater formed of an upper anda lower head 32, 33 between which extends a plurality of tubes 34, sothat the flue gases from the chamber 19 will pass downward through thetubes 34 into the' gas outlet and the stack. The air to be heated entersat the side of the air heater through the duct 35 and passes around theend of the baffle 36 and through the outlet duct 37 this air therebyflowing in a generally upward direction through the air heater, whereasthe hot flue gases pass downwardly through the tubes 34.

Above the head 32 I provide a sprayin means by which the interiorsurfaces of the tubes 34, which are the surfaces contacted by the hotflue gases, may be washed and also sprayed with protective coatingmaterial. In the illustrative embodiment, such a spraying The rate ofheat transfer from the arrangement is illustrated by a tube 38 extendinghorizontally across the chamber 21, the tube 38 being provided withnipples each over one of the tubes 34. The spray tube 38 is mounted in acarriage 39 so that it may be moved laterally across thechamber 21 bymeans of a rack and pinion operated by the chain 39, the tube 38 havinga hose connection 40. Since the tubes 34 are arranged in rows, it isobvious that by moving the tube 38 laterally and bringing it'to restover successive rows, the nipples on the tube 38 may be brought over allof the tubes 34, one row at a time.

By supplying water through the hose 40 and the spray tube 38, theinteriors of the with a protective material in a manner similar to thatdescribed for the arrangement shown in Fig. 1.

The apparatus shown in Fig. 2 will be operated in a mannersimilar tothat described for Fig. 1 and when carrying out my method will have thesame advantages, the washing of the surfaces of the tubes and thespraying of the protective coating being carried on while the boiler is.in operation. In the arrangement shown in Fig. 2, as well as that shownin Fig. 1, it will be understood that the application of the protectivecoating to the surfaces of the heat exchanger is efiected not only bythe direct application of the spray to such surfaces, but also by thefact that the spray is directed in the same direction as the gas flowthrough the heat exchanger, so that the gases pick up and carry theprotective material toall parts .of the surfaces contacted by the gases.

I claim:

1. In a boiler, a flue adapted to conduct hot gases, a heat exchanger inthe flue having tubes each contacted by the hot gases on one of itssurfaces while a fluid is flowing in contact with the other surface,means within the flue to spray a fluid-protective material downwardly onthe surfaces of the tubes, and means for causing the hot gases to flowdownwardly over surfaces of the'tubes exposed to said gases and whilefluid is flowing through said heat exchanger, in order to protect thetubes of said heat exchanger from the corrosive tendencies of saidgases.

2. In a steam boiler, an economizer having tubes and connections wherebywater may be passed through the interior of said tubes, a fluesurrounding the tubes and adapted to conduct hot gases over the exteriorthereof, means within the flue to spray a fluid-protective materialdownwardly on the exterior of the tubes, and means for causing the hotgases to flow downwardly .over surfaces of the tubes exposed to saidgases and while the furnace, and means for introducing to said gases insuccession during their passage to said heat exchanger, a heattransferring liquid anda material for producing a protective coating onthe surfaces of the heat exchanger contacted by said gases to protectsaid heat exchanger from the corrosive tendencies of said gases.

4. In a steam boiler, a chamber having separate compartments in one ofwhich is located liquid-spraying means and in the other of which islocated a heat exchanger,

means to lead the gases from said spraying compartment to said heatexchanger com-.

partment, means for spraying a fluid-protective material downwardly overthe exterior of the tubes of said heat exchanger, and means for causingthe hot gases to flow downwardly over surfaces of the tubes exposed tosaid gases and while fluid is flowing through said heat exchanger, inorder to protect the tubes of said heat exchanger from'th'e corrosivetendencies of said gases.

5. The method of operating a heat exchanger in the gas flue of a steamboiler, which consists in passing gases downwardly over one contactsurface of the heat exchanger and a fluid over the other contact surfaceof the heat exchanger, and spraying a fluidprotective materialdownwardly on the surface contacted by the gaseswhile the gases and suchfluid are flowing, to protect said surface from the'corrosive tendenciesof said gases, said material-being supplied in quantities and at a ratesuflicient to maintain a coating onthe surface exposed to the boilerflue gases.

6. The method of protecting the exterior of a boiler economizer fromcorrosion, which consists in passing hot gases downwardly over theexterior of the economizer and water through the interior thereof andspraying a fluid-protective material downwardly on the exterior of theeconomizer while the gases and water are flowing, to protect saideconomizer from the corrosive tendencies of said gases, said materialbeing supplied in quantities and at a rate suflicient to maintain acoating on the economizer.

7. In' a steam boiler, an economizer disposed in the path of the heatedgases, and means for introducing to said gases in succession duringtheir passage to said economizer a heat transferring liquid and amaterial for producing a protective coating on said economizer toprotect said economizer from the corrosive tendencies of said gases,

the protective material being introduced in the direction of flow ofsaid gases.

8. The improvement in that method of operating a steam boiler in which aheat exchanger is disposed inthe path of the heated gases, whichconsists in successively introducing a spray of a heat transferringliquid and a protective material to the gases during their passage tosaid heat exchanger, the protective material being introduced downwardlyinto the gases in the form of a spray, and the gases flowing downwardlyover said heat exchanger.

DAVID S. JACOBUS.

